1. Technical Field
The present invention relates generally to roof vents for enclosures and more specifically to roof exhaust vent fan assemblies having an electrically powered fan and a hinged cover.
2. Background Art
Roof vent fan devices are known to be used in vehicles as shown in U.S. Pat. No. 1,722,825 to Roethel and U.S. Pat. No. 1,983,979 to Graham and in buildings as disclosed in U.S. Pat. No. 3,479,947 to Myers. The purpose of such prior devices is to exhaust air for cooling and maintaining fresh air in the enclosures. A common disadvantage of prior roof vent fan devices when used in vehicles such as recreational vehicles, motor homes, trucks, vans, tractor cabs, boats and other enclosures having a relatively low ceiling is that they protrude below the ceiling and reduce available head room. This is especially true if the roof is thin in cross-section. In prior devices, wound electrical motors resulted in vent fan devices being substantially greater in vertical cross-section, or thickness, than the roof to which they were assembled, sometimes as much as three times the thickness of the roof in which the devices are installed.
Most vent fan devices have a single speed and are controlled by a simple on/off switch. Multi-speed switches provided for vent fan devices are generally parallel resistance motor speed control switches having one or more resistors which create heat that must be dissipated to prevent melting or deforming the vent fan body near the switch. Previously such switches were installed in the vent fan body below the fan blade in the primary air flow path to achieve the desired heat dissipation. In such vent fan devices the length of the fan housing required to enclose the motor was adequate to receive the switch without adding to the cross-sectional thickness of the device.
These and other problems and disadvantages are overcome by the present invention as summarized below.